Deprotonation of a Hydridoborate Anion.

The first deprotonation of a borohydride anion was achieved by treatment of [BH(CN) ] with strong non-nucleophilic bases, which resulted in the formation of alkali-metal salts of the tricyanoborate dianion B(CN) in up to 97 % yield and 99.5 % purity. [BH(CN) ] is less acidic than (Me Si) NH but a stronger acid than iPr NH. Less sterically hindered, more nucleophilic bases such as PhLi and MeLi mostly attack a CN group under formation of imine dianions [RC(N)B(CN) ] , which can be hydrolyzed to ketones of the [RC(O)B(CN) ] type. The boron-centered nucleophile B(CN) reacts with CO and CN reagents to give salts of the [B(CN) CO ] dianion and the tetracyanoborate anion [B(CN) ] , respectively, in excellent yields.